That would tell you nothing as it is only a proxy to the larger (proprietary) server-side tree library. If you need a read-only tree it is enough if you return tree nodes json exactly as in any other tree server script.

I'm on a Windows 2008 R2 Server with SP1 virtual machine and IE9 Beta installed.
The screencast is under remote desktop but that should not matter as long as all other browsers are working correct, even IE7/IE8 but IE9.

It's all about Browser Mode and Document Mode - I'm totally confused as to what M$ meant by that. It works fine in Browser Mode: IE9 and Document Mode: IE8 Standards. That is what I'm trying to force by

Hi, this error maybe is caused by the new microsoft trend for IE9 to follow only standard functions, standard tags and it's not the only one. Forcing to IE8 compatibility it's a workaround, and it works, but isn't possible to do a fix for this issue?

I have just the same error. But it was not with the checkTreePanel event. It was happened when the mouse pointer was over the tree note. This issue was reproduced with Browser mode: IE9 and Document mode: IE9 standards. I used ExtJs 3.4. There are some reasons, that I can't use the IE8 in the document mode and new ExtJs 4.0. Did you bring this issue to a close? If yes, please, let me know how you could do it. I will appreciate any help. Thank you.